I wrote two objects for doing PWM in Pd, one at message rate, the other at audio rate:

http://at.or.at/hans/pd/objects.html

If you want to know what PWM is:

http://en.wikipedia.org/wiki/Pulse-width_modulation

Of course, these will be included in Pd-extended, and already partially are.

.hc

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¡El pueblo unido jamás será vencido!